Abstract

Establishing how cognitive abnormalities result in the signs and symptoms that define schizophrenia and anxiety disorders (and their co-morbidity) has become a prominent question in clinically, and sub-clinically, applied research. Abnormal performance in schizophrenia, schizotypy and anxiety has been observed in comparison to healthy individuals on a range of cognitive and behavioural tasks. For example, abnormal attention to irrelevant information has long been recognised by clinicians, which has since encouraged researchers to elucidate the nature of the relationship between schizophrenia, and anxiety more recently, with allocation of attention to stimuli in laboratory studies providing empirical evidence for an attentional view of these disorders.

The pre-exposure effect (slower learning to a stimulus that has been rendered familiar by preexposure, relative to a novel cue), hereafter refered to as latent inhibition, has been shown to be inversely correlated with schizotypy, and abnormal in people with schizophrenia, but findings are inconsistent. One potential contributing factor to this inconsistency is that many tasks that purport to measure latent inhibition are confounded by alternative effects that also retard learning and co-vary with schizotypy, such as learned irrelevance (experience of a cue as irrelevant to the occurrence of an outcome due to inconsistent/uncorrelated presentations of a cue and a target). The general aim of this thesis is to address, or begin to address, some of the key questions and limitations with existing research that evaluate latent inhibition and learned irrelevance as potentially useful cognitive endophenotypes for schizophrenia and anxiety disorders. The current experiments separate out the effects of latent inhibition and learned irrelevance to assess the independent effects of these phenomena on schizotypy (and by extension schizophrenia) and anxiety. By teasing apart, the effects of latent inhibition and learned irrelevance the attempt is to disentangle, and improve understanding of attentional abnormalities observed in these sub-clinical traits and by extension, their related pathologies.

Across Experiments 1-4, the purpose was two-fold. The first was to address the limitations of existing latent inhibition tasks by designing a paradigm that examines a purer effect of latent inhibition, by minimising the contribution of learned irrelevance, and assessing how this latent inhibition task co-varies with schizotypy and anxiety (Chapter 2: Experiments 1 and 2). The second was to examine the alternative, potentially less equivocal, learned attentional paradigm (learned irrelevance) and assess the relationship between this task with both schizotypy and anxiety (Chapter 3: Experiments 3 and 4). Based on the assumption that latent inhibition and learned irrelevance share similar psychological underpinnings (in this case, attentional), we anticipated the effect of schizotypy and anxiety to be comparable in the two types of attention tasks here. The results however indicate a double dissociation; an abnormally persistent latent inhibition effect in high positive schizotypy individuals (Experiments 1 and 2) and a reduced learned irrelevance effect in high state anxious individuals (Experiments 3 and 4). The possibility that latent inhibition is non-attentional and the implications of these findings for associative models of attention and learning are explored.

The aim of Experiments 5 and 6 were to explore the causal relationship between induced variations in anxiety (stress, relaxation or neutral mood) and learned variations in attention, using a less ambiguous measure of attention (compared to latent inhibition): learned irrelevance. Based on the findings from Experiments 3 and 4, a reduced attentional bias towards previously established predictive cues was expected in individuals induced with an acute state of anxiousness, relative to individuals induced with either a relaxed or neutral mood state. This pattern of results was observed but to a weaker extent than the previous experiments, suggesting that induced variations in anxiety do not have the same relationship with learning as naturally occurring variations in anxiety, as observed in Experiments 3 and 4. Further analyses revealed that the relationship between reduced learned irrelevance and anxiety was mediated by individuals who were also characterised by high levels of schizotypy, and by extension vulnerability to schizophrenia. Given the potential common underlying cognitive processes to both anxiety and schizophrenia, it seems likely that therapies which target the symptoms of anxiety (e.g., Attentional Bias Modification Treatment; ABMT) would be beneficial to individuals who have also been diagnosed with a psychotic disorder.

This work represents the first attempt to investigate the independent effects of latent inhibition and learned irrelevance on schizotypy and anxiety, using refined tasks that minimised the contribution of either learning phenomenon on each other. How these learning tasks co-vary in patients with schizophrenia and clinically diagnosed anxiety however remains for future research to determine . At this juncture, the current findings lend support to the potential cognitive endophenotype status of learned irrelevance (considering its status as a less ambiguous measure of attention) and its continued use to provide a base for the development of relevant attentional bias modification treatments.